The present invention relates to improvements in the art of plastic bag construction having a flexible fastener structure which incorporates pressure closable but reopenable rib and groove elements. More particularly, this invention relates to an improved method of and means for opening the fastener structure which eliminates the need for pulling apart opposing flaps as has heretofore been necessary.
Reclosable zipper lock plastic bags generally are formed of flexible thin plastic film with front and back walls attached to each other along their sides and along a bottom edge. The bag may be filled through the open bottom edge which is then sealed or may be filled through the top. Adjacent the top edge and extending fully across opposed confronting inner surfaces of the bag walls at the mouth of the bag are a pair of cooperatively interlocking fastener strip profiles formed with respective engageable rib and groove elements made of extruded plastic material. Examples of such bags and means of manufacture thereof are disclosed in U.S. Pat. Nos. 3,198,228, 2,780,261, Nos. RE 28,969, 3,054,434 and 3,340,116. Plastic bags may have the zipper lock rib and groove elements integral with the bags or these zipper lock elements may comprise separate fastener strips which are attached to the tops of bags. In either instance, the zipper lock rib and groove elements normally are extruded and are interlocked during manufacture for convenience of storage and handling. The rib and groove elements then must be separated for filling or for use. Typically, there are flange members extending above the rib and groove elements which flange members are gripped and pulled apart to separate the rib and groove for access to the interior of the bag.
Disadvantages are encountered in this manner of separating the rib and groove elements for opening the bag in that it is often difficult to find and grasp the separate flange elements particularly when the bag is formed of a very thin plastic film. Also, if it is intended that the bags are to be handled by a machine and opened by machine for mechanical handling and filling, it is difficult to provide machine elements which will find and grip the flanges and pull apart the rib and groove elements.